26 Draconis system
From Halopedia, the Halo wiki
The 26 Draconis system us a planetary system that is controled by the United Nations Space Command. This system was one of the first to harbor Insurrectionists. On march 2, 2494, Insurrectionists hijacked the UNSC Callisto and killed the crew (This event is believed to be the start of the undeclared human civil war between the Insurrectionists and the UNSC).
Planets:
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Sources
Halo: Evolutions - Essential Tales of the Halo Universe - The Impossible Life and the Possible Death of Preston J. Cole==